In recent years, starting with electric vehicles and hybrid cars, vehicles equipped with higher-capacity batteries than conventional gasoline vehicles are beginning to proliferate. These vehicles equipped with higher-capacity batteries emit less carbon dioxide than gasoline vehicles when running, and thus have become a focus of attention as one countermeasure against global warming. Also, there is an emerging movement to utilize electric power charged in such vehicles equipped with higher-capacity batteries as an electric power source. The supply of electric power stored in a vehicle to an electric power system is called vehicle to grid (V2G). Utilizing V2G in time periods of high power usage leads to a cut in peak electricity output.
For example, Patent Literature 1 discloses a power supply system that attempts to provide a stable supply of electric power by preregistering a daily required charging amount for an electric vehicle owned by an individual, and using electric power exceeding the daily required charging amount for V2G according to power supply and demand. Also, Patent Literature 2 discloses a network-controlled charging system that controls electric vehicles via a communication network by using network-controlled electrical outlets (Smartlets).
Meanwhile, however, in recent years an increasing number of people are reserving and renting a vehicle as necessary in order to save vehicle upkeep and management costs. In addition to conventional car rental systems, in recent years car sharing, in which a specific vehicle is used jointly by multiple members, is becoming more prevalent.